Geochemistry and origin of metamorphosed mafic rocks from the Lower Paleozoic Moretown and Cram Hill Formations of North-Central Vermont: Delamination magmatism in the western New England appalachians

Coish, R. A.; Kim, Jonathan; Twelker, Evan; Zolkos, Scott P.; Walsh, Gregory J.

doi:10.2475/09.2015.02

Cited by 7 publications

(2 citation statements)

References 71 publications

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“…Following these events, breakoff of the eastwardly subducted oceanic slab at ca. 466 Ma and attendant asthenospheric upwelling resulted in (1) late-stage mafi c rocks with suprasubductionzone signatures that intruded the remnant forearc of the Shelburne Falls arc (Kim et al, 2003;Coish et al, 2015), and (2) the 466.0 ± 0.1 Ma felsic units in the Barnard Volcanic Member of the Missisquoi Formation (a correlative of the Hawley Formation in the Shelburne Falls arc) and time-equivalent volcanic ashes in the Indian River Formation located in the Taconic thrust slices (Karabinos et al, 2017;Macdonald et al, 2017). At about the time of slab breakoff, the bimodal Ammonoosuc Volcanics developed in the Bronson Hill arc, which lies east of the Shelburne Falls arc (Fig.…”

Section: Recent Taconic Plate-tectonic Modelsmentioning

confidence: 99%

Aseismic ridge subduction as a driver for the Ordovician Taconic orogeny and Utica foreland basin in New England and New York State

Jacobi¹,

Mitchell²

2018

Tectonics, Sedimentary Basins, and Provenance: A Celebration of the Career of William R. Dickinson

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Aseismic ridge subduction is common along modern convergent margins. We enumerate six criteria that can be used to recognize aseismic ridge subduction in orogens, including a magmatic gap with uplift followed by bimodal volcanism, which commonly includes explosive, voluminous rhyodacitic volcanism that erupts far from the trench. Features temporally linked with the explosive volcanism include retroarc thrusts and consequent thrust-loaded retroarc foreland basin development. Using these criteria to examine features of the Taconic orogen, together with new stratigraphic and structural data from the Utica basin that constrain the basin subsidence architecture and thrust timing, we propose that at least the older units of the 456-435 Ma Oliverian Plutonic Suite in New England were generated during steepening of the downgoing slab after passage of a subducting aseismic ridge. Weakened crust from delamination and decompression melting promoted westerly directed thrusts (present-day coordinates) that loaded the Taconic retroarc foreland. The resulting Utica basin subsided rapidly and nearly synchronously over an ~150-kmwide region and contains interbedded 453-451 Ma ash layers from the Oliverian Plutonic Suite or coeval plutons to the south. This history of basin subsidence indicates that the major thrust loads that drove development of the Utica basin were emplaced over a similarly brief interval beginning ca. 455 Ma. Thus, the Taconic thrusts, the Utica basin, the volcanic ashes, and the early Oliverian felsic magmatic units could all be related to an aseismic ridge subduction event. Because of the ubiquity of seamount chains, we expect that aseismic ridge subduction affected other segments of the Taconic orogen.

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Section: Recent Taconic Plate-tectonic Modelsmentioning

confidence: 99%

Aseismic ridge subduction as a driver for the Ordovician Taconic orogeny and Utica foreland basin in New England and New York State

Jacobi¹,

Mitchell²

2018

Tectonics, Sedimentary Basins, and Provenance: A Celebration of the Career of William R. Dickinson

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“…For some time, the Bronson Hill arc has been considered to be part of a larger peri-Gondwanan system of arcs that developed in the Iapetus Ocean outboard of peri-Laurentian arcs now located to the west (e.g., Hibbard et al, 2006). Even though the Bronson Hill arc is currently thought to be built on peri-Gondwanan crust, the position of the suture between Laurentia and the western edge of Ganderia, called the Red Indian Line, remains an open matter of debate (Dorais et al, 2012;Macdonald et al, 2014Macdonald et al, , 2017Coish et al, 2015;Tremblay and Pinet, 2016;Karabinos et al, 2017). The Red Indian Line, defined in Newfoundland, is a major terrane-boundary mylonitic fault that separates rocks with North American faunas from rocks with Celtic brachiopods diagnostic of oceanic islands (Williams et al, 1988;Neuman, 1984).…”

Section: ■ Introductionmentioning

confidence: 99%

Geochronology of the Oliverian Plutonic Suite and the Ammonoosuc Volcanics in the Bronson Hill arc: Western New Hampshire, USA

et al. 2019

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U-Pb zircon geochronology by sensitive high-resolution ion microprobe–reverse geometry (SHRIMP-RG) on 11 plutonic rocks and two volcanic rocks from the Bronson Hill arc in western New Hampshire yielded Early to Late Ordovician ages ranging from 475 to 445 Ma. Ages from Oliverian Plutonic Suite rocks that intrude a largely mafic lower section of the Ammonoosuc Volcanics ranged from 474.8 ± 5.2 to 460.2 ± 3.4 Ma. Metamorphosed felsic volcanic rocks from within the Ammonoosuc Volcanics yielded ages of 460.1 ± 2.4 and 455.0 ± 11 Ma. Younger Oliverian Plutonic Suite rocks that either intrude both the upper and lower Ammonoosuc Volcanics or Partridge Formation ranged in age from 456.1 ± 6.7 Ma to 445.2 ± 6.7 Ma. These new data and previously published results document extended magmatism for >30 m.y. The ages, along with the lack of mappable structural discontinuities between the plutons and their volcanic cover, suggest that the Bronson Hill arc was part of a relatively long-lived composite arc. The Early to Late Ordovician ages presented here overlap with previously determined igneous U-Pb zircon ages in the Shelburne Falls arc to the west, suggesting that the Bronson Hill arc and the Shelburne Falls arc could be part of one, long-lived composite arc system, in agreement with the interpretation that the Iapetus suture (Red Indian Line) lies to the west of the Shelburne Falls–Bronson Hill arc system.

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A Laurentian margin subduction perspective: Geodynamic constraints from phase equilibria modeling of barroisite greenstones, northern USA Appalachians

2020

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Phase equilibria modeling of sodic-calcic amphibole-epidote assemblages in greenstones in the northern Appalachians, USA, is compatible with relatively shallow subduction of the early Paleozoic Laurentian margin along the Laurentia-Gondwana suture zone during closure of a portion of the Iapetus Ocean basin. Pseudosection and isopleth calculations demonstrate that peak metamorphic conditions ranged between 0.65 GPa, 480 °C and 0.85 GPa, 495 °C down-dip along the subducted Laurentian continental margin between ∼20 km and ∼30 km depth. Quantitative petrological data are explained in the context of an Early Ordovician geodynamic model involving shallow subduction of relatively young, warm, and buoyant Laurentian margin continental-oceanic lithosphere and Iapetus Ocean crust beneath a relatively warm and wet peri-Gondwanan continental arc. A relatively warm subduction zone setting may have contributed to the formation of a thin, ductile metasedimentary rock-rich channel between the down-going Laurentian slab and the overriding continental arc. This accretionary channel accommodated metamorphism and tectonization of continental margin sediments and mafic volcanic rocks (greenstones) of the Laurentian margin and provided a pathway for exhumation of serpentinite slivers and rare eclogite blocks. Restricted asthenospheric flow in the forearc mantle wedge provides one explanation for the lack of ophiolites and absence of a well-preserved ultra-high-pressure terrane in central and northern Vermont. Exhumation of the subducted portion of the Laurentian margin may have been temperature triggered due to increased asthenospheric flow following a slab tear at relatively shallow depths.

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Geochemistry and origin of metamorphosed mafic rocks from the Lower Paleozoic Moretown and Cram Hill Formations of North-Central Vermont: Delamination magmatism in the western New England appalachians

Cited by 7 publications

References 71 publications

Aseismic ridge subduction as a driver for the Ordovician Taconic orogeny and Utica foreland basin in New England and New York State

Aseismic ridge subduction as a driver for the Ordovician Taconic orogeny and Utica foreland basin in New England and New York State

Geochronology of the Oliverian Plutonic Suite and the Ammonoosuc Volcanics in the Bronson Hill arc: Western New Hampshire, USA

A Laurentian margin subduction perspective: Geodynamic constraints from phase equilibria modeling of barroisite greenstones, northern USA Appalachians

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